AMIRKABIR
Year:2003 | Volume:14 | Issue:56-A|Papers Count:10

In this paper we describe the design and evaluation of Vivaldi elements optimization ‎for operation in the array environment over a wide range of frequency (12-18GHz). ‎The Finite Difference Time Domain (FD TD) is used in design and analysis of finite ‎Vivaldi array and genetic algorithm (GA) for optimization of its radiation pattern. The ‎hybrid method is used to find maximum side lobe level (SLL) over a range of ‎frequency (12-18GHz) by adjustment of the antenna and array parameters. An array ‎SLL improvement of MB was attained by optimization. Here a single Vivaldi antenna ‎and a four-element array are analyzed and compared with measurements. Theoretical ‎and experimental results show good agreement with each other.‎

This paper presents core loss calculation of 3-phase induction motor using finite element method. Three-term iron loss model which separates total core loss into hysteresis eddy currents and excess losses is used. Effect of rotational flux density which exists in some regions of core and flux density harmonics due to nonlinear behavior of core materials and motion of rotor are also included. At the end the calculated and experimental results are compared.

In this paper a novel and accurate method is presented in order to evaluate the series and parallel resistances for detailed model of power transformers. In the proposed method the black box model of power transformers and eigenvalues of its winding are estimated by impulse test. Then the series and parallel resistances can be evaluated for the most upper and lower natural frequencies with the reasonable accuracy to be implemented in the detailed model. The proposed model enables the designers to correct the design data sheets before the mass production by performing the impulse test on the sample benchmark. In present study the comparison between the simulation and test results verifies the proposed method.

A new simple and almost exact image method is proposed for the analysis of ‎horizontal thin- wire antennas above lossy half- space. in this method the half- space ‎is replaced by a few complex images‏ ‏‎.‎ The Generalized pencil of function (GPOF) technique and Summerfield integral ‎representation are used to find the Location and intensity of the current images. ‎similar a dipole sources, a few proper image line sources are obtained for an original ‎line source. the results obtained for the radiation pattern of this equivalent structure ‎are found to practically coincide with the exact results (i. e. those obtained from the ‎Summerfield theory ) compared to the other methods of solution, this method is ‎conceptually much simpler and requires less computing time

This paper presents results of research on isolated connected and continuous Farsi ‎number recognition over telephone. Effect of selecting basic recognition unit (phoneme or ‎word) is investigated and statistical neural and hybrid approaches are compared. In ‎Farsi digit and number recognition continuous density hidden markov models with ‎word and phoneme models embedded reestimation after baum-welch NN and hybrid ‎methods were used Experimental results show that in noisy and telephony conditions ‎the system employing cepstral vectors derived from Mel frequency filter-bank ‎analysis outperforms the system employing cepstral vectors derived from linear ‎prediction ana11sis. also it was observed that performance of HMM system is more ‎than that of both the NN and hybrid systems. The best performance of digit ‎recognition in isolated and connected Farsi digit recognition (with word models) over ‎Farsdigits1 telephony database was %99.1 and %83.7 respectively and the best ‎performance of word recognition in unconstrained Farsi number recognition (with ‎phoneme models) over Farsnumbersl telephony database was %91.1‎‏.‏

In this paper a new method for design and realization of a sinusoidal oscillator is ‎proposed. The oscillator has fixed amplitude. As we know the design of this kind of ‎oscillator is very difficult because of its sinusoidal form and fired amplitude. Design ‎is done in state space domain. After designing oscillator is realized base on the ‎concepts of trees and links. In fact we have designed a nonlinear system such that its ‎phase portrait corresponds to oscillation and also prespecified amplitude of the ‎oscillation. Then it is transferred to the time domain. The design of an appropriate ‎nonlinear system is based on the equipotential curves.‎

In this paper a new method based on multistage fuzzy control using intelligent ‎optimization techniques is proposed to optimize the automatic train control system. In ‎this method the energy function which elaborates the train power consumption is first ‎minimized by applying Kuhn Tucker conditions. As a result the switching points at ‎which the control strategies are changed between acceleration coasting constant speed ‎and braking are determined considering the track specifications including gradients ‎and curvatures as well as the practical train model. Since in constant speed strategy ‎the energy optimization leads to infinite changes in control inputs which is not ‎practically possible a multistage fuzzy control based on fuzzy dynamic programming ‎with fuzzy termination time is incorporated to overcome this difficulty. Multistage ‎fuzzy control will optimize other significant goals involving safety traceability in ‎speed and accuracy in distance and limit the number of switching among different ‎strategies. Hence the method will satisfy the practical requirements. This method ‎considers the running time between two stations as independent and controllable ‎variables therefore the calculated strategies are very useful and appropriate for traffic ‎control which the time regulations make a vital and important role. The simulation ‎results will demonstrate the efficiency of proposed method.‎

It is known that interaction of pulsed lasers with tissues can cause acoustic signals ‎within the tissue. These laser - induced signals can be detected in a contact and non -‎contact modes such as in interferometry in order to obtain some information regarding ‎interaction mechanism absorption coefficient of tissue and on - set of ablation ‎process. In this article a broad review and modeling of IR and UV laser interaction ‎with ophthalmological tissue is presented.‎

A cellular learning automaton (CLA) is a collection of learning automata arranged in a ‎grid similar to cellular automata and interacts with each other. Each learning automaton ‎based on the actions chosen by their neighbors tries to find its best action in order for the ‎cellular learning automata to reach a particular goal. In this paper several applications of ‎cellular learning automata to designing image processing operations such as noise ‎removal image segmentation and feature extraction are presented. The proposed ‎algorithms have number of good characteristics such as: effectiveness in the presence of ‎noise higher accuracy .comparing to other image processing algorithms parallel nature ‎and locality.‎